States seek exemption for Denim

Officials with the Mississippi Bureau of Plant Industry are hopeful EPA will act quickly to approve their request for cotton growers to use the pesticide emamectin benzoate (Denim) for the control of beet armyworms and resistant tobacco budworms.

The request to EPA for an emergency exemption use permit, also known as a Section 18, was made early in the year in order to obtain approval in time to benefit those cotton producers battling high populations of the insects this summer.

Following on the heels of Mississippi, state officials in Texas submitted their request to EPA for a Section 18 exemption for Denim on March 5. The Texas Department of Agriculture says it too submitted Section 18 requests earlier than usual to insure adequate supplies of pesticides for the control of beet armyworm outbreaks.

Tommy McDaniel, branch director for the Mississippi Bureau of Plant Industry, says he also expects officials in Arkansas and Louisiana to follow Mississippi's lead. In Arkansas, State Plant Board Director Mike Thompson says, We've had some interest expressed in obtaining a Section 18 for Denim, but no formal action has been taken as of yet.

The reason for Mississippi's exemption request, McDaniel says, is that beet armyworm outbreaks have caused serious yield losses in past years and that involvement in the boll weevil eradication effort increases the risk of serious outbreaks occurring.

Should a severe beet armyworm outbreak occur in 2001, supplies of effective beet armyworm products, such as Tracer, Intrepid and Steward, may be depleted, McDaniel says. Also, because avoiding repeated use of the same product is the key component of insecticide resistance management, producers need access to as many effective beet armyworm products as possible.

As we enter the 2001 growing season, risk of beet armyworm outbreaks are a key concern for growers. Although the winter of 2000-01 has been relatively severe, beet armyworm moths are strong fliers and can quickly re-invade from more southern areas even if no overwintered insects survived in the state, McDaniel says. Also, all of Mississippi will be involved in boll weevil eradication in 2001. Because of the high use of ULV malathion sprays and the adverse impact these have on beneficial insect populations, boll weevil eradication efforts are known to greatly exacerbate risks of beet armyworm outbreaks.

A severe outbreak of beet armyworms would, according to the state's exemption application, result in the treatment of at least 750,000 cotton acres statewide. In the event of an outbreak of resistant tobacco budworms, McDaniel estimates that a minimum of 400,000 acres of non-Bt cotton could require treatment.

Resistance to synthetic pyrethroid insecticides was first detected in Mississippi tobacco budworm populations in 1985. Since then, levels of pyrethroid resistance have increased and researchers have documented high levels of resistance to the organophosphate and carbamate classes of insecticides as well. Consequently, ability to control outbreaks of tobacco budworms with these products has deteriorated, he says.